Thermostatic switch for electrical heating devices



F. KUHN Dec. 3 l 1929.

THERMOSTATIC SWITCH FOR ELECTRICAL HEATING DEVICES Filed Dec. 21, 1926 wumdoz 17 4711 Avlz 85% Wm M Patented Dec. 31, 1929 UNITED STATES PATENT OFFICE FRANK KUHN, OF DETROIT, MICHIGAN, ASSIGNOR TO AMERICAN ELECTRICAL HEATER COMPANY, OF DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN Application filed December 21, 1926. Serial No. 156,153.

The invention relates to thermostatic switches for electrical heating devices and is an improvement on an earlier Patent 1,107,-

316 issued August 18, 1914. I

k The construction forming the subject matter of the above patent comprises a switch for controlling the current of an electrical heater, means for automatically opening said switch, friction means for restraining the movement of said automatic opening means and an expansible element for relieving the friction when the temperature rises above a predetermined limit. The present inven tion also comprises these broad elements and 5 in addition other features including, first, thermostatic means which will more accurately control the opening of the switch; secportion of an electrical heater such as a laundry iron to which my improvement is applied.

Figure 2 is a perspective view of the operatingmechanism with the supporting frame broken away. 1 I Figure 3 is a plan view of the switch and portions of the mechanism outside of the hood of the heater and I I Figure 4 is a plan view of the thermostat and associate devices within the same.

While my improved switch is applicable to various electrically heated devices as shown it is applied to a laundry iron in which A is the base of the iron, B the heating unit applied thereto, C the clamping plate for 5 securing said unit to the base and D the hood for enclosing a unit and clamping plate and providing an air chamber thereabove for heat insulation. My improved switch is 7 preferably constructed as a unit which ma heater and as specifically shown is, of the following construction:

E is a snap switch of any suitable construction not shown in detail having the terminals F and G and an operating rock arm H together with means not shown for producing a snap action. This switch is mounted on a plate or frame I arranged preferably out side of the hood D. Upon the same plate is secured a depending lframe J which extends downward through an aperture in the hood into a position in proximity to the clamping plate C to be under direct radiation of the heat therefrom. is a rotary member preferably journaled in center bearings K, K onthe frame J and an upward extension J thereof which'is above the plate I. L is a ratchet wheel mounted on the portion of the shaft K which is above the plate I and M is a brake drum mounted on the portion of the shaft below said plate. N is a brakeshoe bearing against the periphery of the drum M and is a composite thermostatic bar forming an arm attached to said brake shoe and having its opposite end anchored to a bracket P rising from the frame J. Q is a set screw engaging a bracket Q on the frame J and adapted to bear upon the arm 0 to adjust the braking pressure applied by the shoe N to the drum M. Above the plates I there is arranged a member R having one end pivotally attached to the rock arm H and at its opposite end a pawl or dog R for engaging the ratchet wheel L. The member R has also attached thereto the spring S having its opposite end anchored at S said spring placing the tension on said member R in a direction which would cause the awl R engaging the ratchet teeth to rotate t e wheel L and drum M. Such movement is however resisted by the braking friction of the shoe N on the. drum M so that in the closed position of the switch E the parts are in the position shown in full lines in Figures 2 and 3. The member R is also provided with an upwardly extending finger piece R which when pressure is applied thereto will disengage the pawl R from the ratchet wheel L permitting the spring S to actuate the member R and through y it the rock arm H to open the switch. be attached to thls or any other electrical With the construction as described, in setting the switch the screw Q is so adjusted that the braking pressure of the shoe N upon the drum M is suflicient to resist the actuation of the member R by the spring S both when the parts are cold and when heated below a predetermined temperature limit. However, the increase in temperature will cause the warping of a thermostatic bar 0 and when the temperature limit is exceeded this warping will sufliciently relieve the friction of the shoe N upon the drum M to permit the spring S to actuate the member R. This, by opening the switch E will out off the heating current thereby avoiding any further rise in temperature. The same switch E may be used for manually controlling and cutting off the current where the temperature is below the limit by pressing upon the finger piece R which, withdrawing the bolt R from its engagement with the ratchet wheel L, releases the member R and permits the spring S to actuate the same and the switch.

What I claim as my invention is:

1. In a heater, an automatically opening electric switch for controlling the heater, thermostatic means controlling the opening of said switch comprising a brake drum, a shoe engaging said drum, a composite thermostatic bar to which said shoe is attached and means for tensioning said bar to press said shoe against said drum, said tension being relieved by the warping of said bar to release the brake.

2. In a heater, an automatically opening electric switch for controlling the heater, thermostatic means for controlling the opening of said switch comprising a brake drum, a brake shoe engaging the same, a composite thermostatic bar to which said shoe is attached and through which said shoe is pressed against the brake drum, said bar being adapted to be warped by increase in temperature in a direction to relieve the pressure of said shoe on said drum and adjustable means for varying the initial tension on said bar whereby the temperature at which the brake is released may be varied.

3. In a heater, an automatic electric switch for controlling the same, thermostatic means for controlling the automatic operation of said switch comprising a brake drum, a brake shoe engaging the same, a composite thermostatic bar attached to said shoe and constituting a resilient arm for applying pressure against said drum, said pressure being relieved by the warping of the bar through temperature change and means for adjusting the initial tension of said bar on said shoe to vary the temperature point at which the brake is released.

4. In a heater, an electric switch for controlling the same, means for automatically opening the switch, locking means for preventing the operation of said opening means, thermostatic means for releasing said locking means on the attainment of a predetermined temperature, and means associated with the,locking means for varying the temperature point at which the thermostat operates to release the said locking means.

5. In a heater, an electric switch for controlling the same, means for automatically actuating said switch including a rotatable member and a thermostatic bar normally under tension and engageable with said rotatable member for preventing operation of said switch actuating means and means for varying the tension on said bar whereby the temperature at which the thermostatic bar operates to release said rotatable member may be varied.

6. In a heater, an electric switch for controlling the same, means for automatically actuating said switch, a rotatable member controlling the operation of said means, and temperature responsive means normally exerting a pressure upon said member to prevent rotation thereof.

7. In a heater, an electric switch having an arm, a pawl connected to said arm, a ratchet wheel engageable with said pawl, means acting upon said pawl tending to rotate said wheel and open said switch, and temperature responsive means including a thermostat having a flexible strip operable to control the operation of said wheel for controlling the operation of said wheel.

8. An electric iron having a heating element, a hood concealing the heating element, an electric switch positioned exteriorly of the hood, means for automatically actuating the switch, a locking means for preventing the operation of said automatic means and thermostatic means operable to release said looking means upon the attainment of a predetermined temperature.

-9. In a heater, an automatically operable electric switch for controlling the operation of the heater, heat insulated means interposed between said heater 'and switch, looking means for holding said switch in closed position, thermostatic means arranged to be under the direct heat from said heater and adapted to release said locking means upon the attainment of a predetermined temperature and means for varying the temperature point at which the thermostatic means is adapted to operate to release the locking means.

10. In a heater, an electric switch for controlling the same, means for automatically operating said switch, a rotatable member controlling the operation of said automatic means, and a thermostat having a temperature responsive member positioned adjacent the rotatable member and operable at a predetermined temperature to exert a pressure upon the rotatable member for preventing rotation of the latter.

11. In a heater,'an electric switchv for controlling the same, means for automatically operating the switch, locking means for preventing the operation of said actuating means, and temperature responsive means including a thermostat having a thermostatic strip positioned adjacent the locking means aforesaid and operable to control the operation of the latter.

12. In a heater, an electric switch for controlling the same, means for automatically actuating the switch, locking means for preventing the operation of said actuating means 7 includlng a rotatable member and a thermostat having a strip responsive to variations in temperature and adapted to engage the rotatable member for controlling the operation of the same.

In testimony whereof I aflix my signature.

. FRANK KUHN. 

